The invention refers to a tool for an ultrasonic welding device, covering a working surface limited preferably by a compression chamber, as well as empty surfaces running in particular perpendicular to this, such as a front surface. In particular, the invention refers to a tool in the form of a sonotrode, which transfers ultrasonic oscillations for welding metals with ultrasonic oscillations running in the direction of the sonotrode's longitudinal axis, whereby the front surface runs perpendicular to the working surface of the sonotrode, which runs from their sonotrode heads respectively.
When assembling materials using ultrasound, the energy needed for welding is in the form of mechanical oscillations into the welding material, whereby the tool, which is also designated a sonotrode, is coupled with the part to be joined, which is immigrated toward it and moves it. At the same time, the parts to be joined are compressed onto one another by a static welding strength. Welding of the parts to be joined takes place through the interaction of static and dynamic forces, without which additional materials would be required.
Both plastics and metals can be welded by means of ultrasound. The mechanical oscillations are aligned parallel to the joined surface. This results in a complex relationship between the static strength, the oscillating shearing force, and a moderate temperature rise in the welding zone.
For this, the workpieces are arranged between the vibrating sonotrode and a static backplate electrode, which can be designed in a multipart format, in order to limit the sonotrode, i.e. the working surface of their heads of a compression chamber. This can be designed in two directions running perpendicular to each other, in particular height and width, as in EP-B-0 143 936 or DE-C-35 08 122. Thereby, an alignment to the cross sections results from conductors to be welded, for example.
In order to obtain reproducible welding results of high quality, the deflection of the sonotrode should take place predominantly in the longitudinal direction alone, thus in the direction of the ultrasonic oscillation, without which a deflection takes place perpendicular to this to a noticeable extent.
The known sonotrodes exhibit front surfaces bordering working surfaces. According to construction, a high deflection of the working surface takes place perpendicular to the sonotrode's longitudinal axis in relation to the deflection in the direction of the sonotrode's longitudinal axis. Thereby, the disadvantage results that the working surface can run bent to the sonotrode's longitudinal axis, so that a gap can be formed between the working surface and the available parts, which run parallel to the sonotrode's longitudinal axis.